The exchange and maintenance of genetic information in Escherichia coli will be studied employing biochemical and genetic techniques. Enzymes known to be involved in genetic recombination such as exonuclease I, exonuclease III and exonuclease V will be amplified in vivo by construction of recombinant ColEl plasmids. These enzymes will be subsequently purified and antiserum prepared against them. Cooperative interactions between exonuclease I, exonuclease III, exonuclease V and DNA polymerase I will be studied in vitro employing homogeneous enzyme preparations. The specificity and amount of residual exonuclease I activity in recB- sbcB- and recB- xonA- strains will be examined to account for the observed phenotypic differences. Employing specially constructed nuclease deficient strains, attempts will be made to identify and purify the gene products associated with recF, recL, uvrD, and uvrE using affinity chromatography techniques. Exonuclease VIII will be purified to homogeneity and studied in more detail. Additional mapping studies will be carried out with recJ, recK and xth mutants to determine the precise nature of these loci. The roles of exonuclease I, exonuclease III and exonuclease V in maintenance of ColEl plasmids will be examined employing genetic biochemical and physical analysis of nuclease deficient strains carrying ColEl and its drug resistant derivatives. Conditionally lethal mutants of E. coli which map between recB and recC will be studied in vivo empolying pulse-labeling experiments and specific inhibitors of DNA and RNA synthesis. Exonuclease V activity obtained from these mutants will be examined for altered substrate specificity. The involvement of host functions in the translocation of DNA sequences will be studied by constructing Pl cam clro100 lysogens of a set of isogenic strains carrying a variety of mutations which affect DNA metabolism. Loss of the TnC transposon will be examined in both lytic and lysogenic growth.